tailieunhanh - Ebook Tiếng Anh chuyên ngành kỹ thuật xây dựng: Phần 2

Nối tiếp nội dung của phần 1 cuốn sách "Tiếng Anh chuyên ngành kỹ thuật xây dựng", phần 2 trình bày các bài học về 9 bài học thêm về các lĩnh vực xây dựng, từ công tác khảo sát, trắc đạc, nền móng, xử lý móng, ván khuôn, cốt thép, đến chống thấm và chống sét công trình. . | Lesson 12. TUNNELS Most of the tunnels before the great age of railroad construction were built in connection with mines water supply systems or canals. As we noted the maximum grade at which a steam locomotive could operate efficiently was 2 percent. This fact encouraged the construction of a great many tunnels. As more tunnels were built many significant technical advances were made in boring both through underwater clay and through rock. One of the most remarkable tunnel building feats was the construction of the first tunnel under the Thames River in London. This tunnel is still used by the London Underground Railway System. It was dug out of clay beneath the riverbed between 1825 and 1843 under the direction of Sir Marc Brunel who had designed a tunneling shield that made the work possible. The shield offered the workers protection while they dug out clay and mud in the face of the shield. It was the moved forward by jacks so that the process could be repeated. One of the first major tunnels built through rock was the Mont Cenis Tuneel in the Alps between France and Italy. It is fourteen kilometers long and was built between 1857 and 1871. When construction began on it progress was only twenty-two centimeters a day. Fortunately the pneumatic drill which uses compressed air to bore holes in rock was invented a few years after construction began. Thereafter the tunneling speed was increased to two meters a day. Like most tunnels the Mont Cenis was bored from two different headings one in France and one in Italy which met in the middle. Another tunnel under the Alps the Simplon remains a major engineering accomplishment. It runs for a distance of nineteen kilometers and at one point it is more than 2 100 meters under 216 the crest of a mountain. It was built between 1898 and 1906 and extraordinary difficulties had to be overcome extremely high temperatures rock that burst off the walls because of the pressure springs of both cold and hot water and layers of soft

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